Peter Macejko, a Wireless Specialist at Anritsu, paired Otii Arc with a network simulator MT8821C to analyze the power consumption of cellular IoT systems. Testing the battery drainage in an IoT device during different radio communication states, in a repeatable, controllable and automated way, is invaluable for securing the product quality throughout the development project.
“In general, the most significant impact on a battery is the peak performance of a device and the power saving mode (PSM) in which an IoT device is most often placed”, says Peter.
The main goal was to import a signaling trace from the Anritsu instrument to the Otii GUI application, to understand the effects of the device energy consumption in the different radio scenarios. Creating an automated way of measuring power consumption while verifying the device’s network capabilities meant using the following:
MT8821C is connected to the PC via the Ethernet cable, allowing the remote control of the instrument. Otii Arc is used as a power analyzer. Its server runs locally on the PC, which is connected to the Otii Arc via a USB cable.
Otii application and its GUI is used to show the energy consumed. During a measurement, the energy consumption is shown in real-time. It can be recorded and processed later as needed.
Both instruments are automated using Python. To control the MT8821C, the PyVisa module is installed on the PC, in addition to Python itself. It provides the PC with all the necessary tools to communicate with the network simulator using Virtual Instrument Software Architecture (VISA) commands and queries.
The communication for and the control of the Otii Arc is provided by an API library offering a large number of functionalities. Note that the repetitive steps used in the Otii GUI application can be automated using Python. Otii Enterprise license enables access to these scripting functionalities.
Few things to consider, according to Peter, when addressing this type of automation:
And the result? Once the signaling trace is imported and the time offset between the record and the signaling trace’s timestamp is adjusted, signaling stages of the radio communication can be seen inside the Otii GUI application, synced to the measurement. As an example, Fig. 2 shows the power consumption when a device under test (DUT) joins the network. By clicking on the imported signaling trace line in the log window of Otii, it automatically connects to the power consumption in the above graph and the current level at that specific time.
In this project, a DUT is continually supplied with a constant voltage power by Otii Arc.
“In the real world, IoT devices usually have batteries that are unable to hold a constant voltage over the lifetime of the device. Therefore, to enhance the fidelity of the measurement, I recommend using Otii Arc (and Otii Battery Toolbox) to simulate different batteries’ power profiles.”, Peter adds.
Using Otii Arc and Otii Battery Toolbox, different batteries can be emulated, ranging from commercial batteries to those of customized design.
If you are interested in Anritsu´s Python script and want to know more about the use case, get in touch!
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